In recent years, there have been remarkable advances in gasoline engines and various types of mechanisms having been applied and then the improvements of the fuel consumption of vehicles with gasoline engine have been astonishing. The driving forces for this can be classified into the two areas, and one is increasing of the combustion efficiency by higher compression ratios and improving charging efficiency, and the other is the reduction of the mechanical frictional losses.
The mechanisms for increases in combustion efficiency, by means of compression ratios and charging efficiencies are achieved by combining with direct injection mechanisms, in which gasoline is injected directly into the combustion chamber, and an Atkinson cycle, in which the expansion stroke is longer than the compression stroke, and for the above, exhaust gas recycling devices as well as variable valve-timing mechanisms are used.
In contrast with this, countermeasures for mechanical friction losses in the engine are achieved by way of two methods, which reduces the mechanical friction losses by way of the actual mechanisms and which depends on improved lubrication.
Reduction of friction loss by way of the actual mechanisms have already been taken to the limit, and as the result, by using supercharger systems for example, smaller displacement engines can be obtained greater output, it extends to the downsizing of the engine which controls a mechanical loss per output. In this case, because greater output is achieved with a smaller piston, it is a matter of course that the frictional resistance between the piston ring and the cylinder wall is greater than that of a conventional natural aspiration engine of the same displacement. Consequently, while higher lubrication performance is required, inevitably the internal frictional resistance becomes higher.
As the other device in countermeasures, reducing frictional loss between the piston ring and the cylinder wall by reduction of piston ring tension as less as possible is known as one trend. This is primarily used in natural aspiration engines. This kind of natural aspiration engines often use engine oils with lower viscosity and less agitating resistance. However, the oil film between the piston ring and the cylinder wall become thinner and the frictional resistance between these is conversely high.
Such mechanical systems are widely employed in engines, but in all of the systems used to achieve these characteristics, such as EGR and variable valve-timing mechanisms, direct injection, and other mechanisms, engine internal deposits occur more easily than in conventional engines, and thus these engines became more sensitive by secular change.
In case of engine oils, there is an effort to improve the friction reduction by means of lowering its viscosity and by using more friction modifier. However, just by increasing the amount of friction modifier lease to form the sludge in engine oil. Conversely, with a limited amount of friction modifier, the friction modifier consumes by driving distance and times, and the fuel saving effect of it gradually fades. The ILSAC, which establishes the fuel consumption improvement rates for international oil standards, has standardized fuel consumption improvement rates after 16 hours and after 96 hours, and every upgrade the specification, the fuel economy performance is required to be more longer duration, and the specification became more severe which requires more longer lubricity durations by way of improvements of engine oil formulations, but technology has still not been established which would allow for sufficient improvements in fuel economy over the entire life of the engine oil.
In order to compensate for these unsatisfied performance, by adding lubricity improver in to gasoline fuel, the making up technique for the lubricity performance of engine oil all the time has been introduced (more than 4% of improvement of the fuel consumption by adding friction modifiers into fuel were reported in the Bulletin of the 7th Fuel and Lubricating Oil Asia Conference.). However, in case of using one kind of lubricity improver or, the combination of several lubricity improvers, deposit of the intake system and intake valve deposit as well as combustion chambers deposit surely increase more than nothing.
Therefore, gasoline compositions together with detergent and friction modifiers have been introduced, for example, such as polybutenylamines, polyetheramines are used as the detergent. However, the combustion chamber deposit, which affect most on aging deterioration of engine performance, can be only effected by polyeteramine detergency.
The friction modifiers which put together with detergents are amines, amides and esters. Many ester-based friction modifiers, which are the most effective type among them, have been introduced, but ester-based friction modifiers cannot be stored for a long term together with detergents (particularly polyetheramine) due to internal reactions. s Because of the ester decomposition, for example, that the friction reducing effect cannot be maintained, and thus it is necessary to handle the friction modifiers and the detergent separately, or these to be added into the fuel immediately after the blend. Therefore, no formulations have been made which mix ester-based friction modifiers and detergents (for example, polyetheramines) together.
Technologies for improving fuel efficiency are known, not only in gasoline engines, but also in the most recent diesel engines, and are claimed (for example, see Patent Literature 1), but these are just only effect on the friction reduction of the engine internal parts (between the cylinder wall and the piston ring), and these technology have not yet obtained fully satisfactory effects on the practical fuel consumption, and thus there is a demand for better technologies, in diesel engines as well.